Technical Field
The technical field relates to a member for dissipating heat of an electronic component. In particular, the technical field relates to a member for dissipating heat of an electronic component (heat-generating component) that generates heat in a housing of an electronic apparatus, a precision apparatus, or the like.
Description of Related Art
Recently, along with an improvement of performance of electronic apparatuses such as mobile phones or laptops, the heat generation density of a heat-generating component has rapidly increased. For electronic apparatuses, thermal diffusion members have been required. In particular, there are many occurrences in which small mobile apparatuses come into direct contact with the human body. Therefore, an increase in the outer surface temperature of a housing of such a small mobile apparatus causes problems.
One of the problems caused by the increase in the outer surface temperature of a housing of a mobile apparatus is a low-temperature burn. The low-temperature burn is a burn caused when the human body is exposed to a temperature higher than the body temperature for a long period of time. The human body is burned when exposed to a temperature of 44° C. for 6 hours. A report shows that, as the temperature increases by 1° C., the time taken for the human body to be burned is reduced to half.
Unlike common burns, in the case of the low-temperature burn, the patient recognizes the progress of the symptom late in most cases. When the patient recognizes the progress of the symptom, the skin is severely burned in many cases. Recently, many medical cases have been reported in which, when a small laptop is used on the lap for a long period of time, a low-temperature burn is caused. In the future, since small and mobile apparatuses will be increasingly developed, the most important issue is to suppress the surface temperature of an apparatus to a low temperature by even 1° C.
As a method of preventing an increase in the surface temperature of an apparatus, JP-A-2009-111003 discloses a configuration of providing a sheet, in which a graphite sheet and a heat insulating material are laminated, between a heat-generating component and a housing. FIG. 6 illustrates a composite sheet 50 having this configuration.
A component 11 is mounted on a substrate 10. A thermally conductive layer 12 and a heat insulating layer 13 are laminated on the component 11, and a housing 14 is positioned thereon.
Heat generated in the component is diffused in the thermally conductive layer 12. The heat diffusion stops in the heat insulating layer 13. As a result, the heat is not locally conducted to the housing 14.
Accordingly, when the housing 14 is touched by a hand, local heat is not detected.